In their simplest form, 3-substituted-3,4-dihydro-2H-1,3-benzoxazines (hereinafter referred to as 3-substituted benzoxazines) are compounds containing the following structural unit:
wherein R represents a monovalent organic group. In many cases, they are further substituted at one or more of the ring carbons. In those cases wherein R contains one or more aromatic groups, the 3-substituted benzoxazines may be highly viscous or even solid under ambient conditions.
3-Substituted benzoxazines typically homopolymerize at elevated temperature, and may be typically cured at lower temperature using a polythiol. For example, PCT Published Patent Application WO 2010/141396 A1 (Gorodisher et al.) describes benzoxazine-thiol adducts which may be cured to produce compositions useful in coatings, sealants, adhesives, and other applications. Similarly, PCT Published Patent Application WO 2009/115586 A1 (Burns et al.) describes adducts useful for improving the toughness and curable compositions using such toughening adducts.